'Flying saucer' airbag for Mars splashes down in Hawaii

Hauled from the sea like an oversized jellyfish, this soggy saucer could one day drop humans on the dusty surface of Mars.

On Saturday, NASA lifted the doughnut-shaped airbag high over the Pacific Ocean and then let it fall back to Earth, testing an inflatable system for putting human missions on the Red Planet.

Most successful robot landings have used some combination of parachutes, airbags and retro-rockets to safely slow the descent from the edge of Mars's thin atmosphere to its rust-coloured surface. And in 2012, the 1-tonne Curiosity rover pioneered the ambitious "sky crane" system, which lowered the rover to the surface on tethers suspended from a hovering platform. But human missions will need to bring tens or hundreds of times more mass to the surface in one trip, and existing technologies do not scale up well.

Ripped chute

The Low-Density Supersonic Decelerator is an inflatable system that reduces speed on the way down without adding lots of mass. The system would also use an enormous parachute twice the size of Curiosity's.

After a series of weather delays, NASA completed the first test flight on 28 June. The team lifted the system into the air above a missile range in Hawaii using a high-altitude balloon. The craft then used rockets to propel itself to an altitude of 55 kilometres, where atmospheric density is closer to that around Mars, before plummeting into the sea. "The delays were due to unfavourable winds that would have carried the balloon and vehicle over populated areas," says team member Mark Adler at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.

This flight was meant to test just the rockets, but they performed so well that the team also deployed the saucer-shaped airbag and parachute. The airbag slowed the vehicle from about Mach 4 to Mach 2.5. The parachute, however, did not fare so well.

"It showed damage early in deployment, which the supersonic flow eventually turned into a lot of damage, destroying the parachute," says Adler. The team will examine the recovered chute as well as high-speed video of the drop to figure out what went wrong and redesign the parachute in time for more tests early next year, he says. But overall, he is pleased with the results.

"The successful test flight is a major milestone for landing heavier payloads on Mars," says Allen Chen, also at JPL. "The project has successfully invented and demonstrated a method for testing technologies that we're going to need to push Mars exploration forward."

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